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Goodstein: termination through hereditary base change and ordinal descent

Contribution grade

Ordinal analysis and number theory · Exact theorem and reusable mathematical method

Reference score230,000Provisional editorial estimate of this exact contribution; its grade is assessed separately.

What changed

Goodstein connected natural-number descent processes to ordinal notation below epsilon zero. Writing numbers hereditarily in a base, replacing that base throughout the nested exponents by the next prescribed nondecreasing base, and subtracting one produces a process that eventually reaches zero. Replacing the finite base by omega assigns a strictly descending ordinal whenever the current number is positive. The paper relates these arithmetical processes to a restricted ordinal well-foundedness principle and develops finitary termination arguments for restricted ordinal heights.

Scientific scope

Goodstein connected natural-number descent processes to ordinal notation below epsilon zero. Writing numbers hereditarily in a base, replacing that base throughout the nested exponents by the next prescribed nondecreasing base, and subtracting one produces a process that eventually reaches zero. Replacing the finite base by omega assigns a strictly descending ordinal whenever the current number is positive. The paper relates these arithmetical processes to a restricted ordinal well-foundedness principle and develops finitary termination arguments for restricted ordinal heights. The general ordinal-descent proof uses well-foundedness below epsilon zero; the paper's explicit finitary arguments cover restricted heights, not one uniform primitive-recursive termination bound for every starting integer. Arbitrary prescribed base functions and the fixed successive-base first-order PA sentence must be distinguished. The 1982 unprovability theorem is a separate contribution and is not backdated to1944. Change-base-then-subtract and subtract-then-change formulations are related in the paper but are not identical trajectories.

Evidence

The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. The general ordinal-descent proof uses well-foundedness below epsilon zero; the paper's explicit finitary arguments cover restricted heights, not one uniform primitive-recursive termination bound for every starting integer. Arbitrary prescribed base functions and the fixed successive-base first-order PA sentence must be distinguished. The 1982 unprovability theorem is a separate contribution and is not backdated to1944. Change-base-then-subtract and subtract-then-change formulations are related in the paper but are not identical trajectories.

Contributors

Provisional WRS assessment, edition 2026-10-23.3. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.

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